Recently, an image forming method is utilized in almost image forming apparatus to form a high quality image in high speed, in which a static image is formed on an image forming member and is developed by a toner, and thus obtained image is transferred onto an image supporting material and fixed by contacting with a heating means.
In such the image forming method, there is a problem of that deformation of the image is the step of transferring the image developed by the toner to the image supporting material.
As a countermeasure to such the problem, various methods have been proposed such as a sticking transfer, however, have drawbacks regarding the high speed treatment ability, and sufficient transfer efficiency cannot be obtained when the amount of the toner to be transferred is too large. Particularly, it is difficult to entirely transfer the toner image of a color image since the toner amount in the color image is larger than that of a conventional monochromatic image. Consequently, such the problem is become important in the color image formation.
Besides, as a method for improving the transfer utilizing an electric field, a method is proposed in which ultrasonic wave is applied in the occasion of the transfer to raise the transfer efficiency, cf. Japanese Patent Publication Open to Public Inspection No. 2001-100546. This method is effectual since the unevenness of the toner can be avoided and high efficiency transfer can be carried out. In such the method, however, defects are formed sometimes on the image forming member, hereinafter also referred to as the photoreceptor because the image forming member is the photoreceptor in almost cases, and the solution of such the problem has been demanded.